Digital calibration method and device for R-2R digital-to-analog converter

Abstract

The present invention discloses a digital calibration method and device for an R-2R digital-to-analog converter, wherein the method includes: connecting each unit conversion unit between detection circuits to obtain a detection output signal corresponding to each unit conversion unit; obtaining the actual resistance value in each unit conversion unit based on the detection output signal and forming a resistance value set; obtaining a target output voltage based on an ideal digital input signal and an ideal resistance value set, and obtaining the actual digital input signal corresponding to each unit conversion unit when the error between the target output voltage and the actual output voltage is minimized through a minimum mean square error algorithm; thereby obtaining the calibrated actual output voltage, with the minimum error compared to the ideal output voltage. The present invention greatly reduces the accuracy requirements for analog device matching, making it possible to design low-cost digital-to-analog converters using advanced processes, and using relatively inexpensive devices to achieve digital calibration of R-2R digital-to-analog converters.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit design, and in particular to a digital calibration method and device for an R-2R digital-to-analog converter. Background Art

[0002] A digital-to-analog converter (DAC) converts a digital signal, which is discrete in amplitude and time, into an analog signal, which is continuous in both time and amplitude. With the advancement of informatization, this functional module has become an essential component in many electronic systems.

[0003] The accuracy of a digital-to-analog converter (DAC) is a key performance indicator. It determines the amount of distortion and noise generated during the conversion process. The resistor ladder DAC (Resistor Ladder DAC) is one of the simplest DACs currently available. Its simple structure, low power consumption, and low noise make it a key component of DACs.

[0004] With the development of integrated circuits, more and more digital-to-analog converters are being integrated into systems-on-chip (SoCs). This requires more streamlined design approaches for DAC circuits to reduce costs. At the same time, it is also necessary to minimize component deviations and mismatches caused by the manufacturing process. In the manufacturing process of DACs, to improve the accuracy of resistor ladder DAC circuits, existing technologies typically use expensive laser calibration equipment to calibrate components on the calibration chip, or design redundant components into the circuit to achieve error calibration. Therefore, to reduce costs and meet process accuracy requirements, existing SoCs typically do not use resistor ladder DAC circuits in chip design. Instead, SoCs typically use other types of conversion circuits that are less sensitive to process requirements, such as Sigma-DeltaDACs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the manufacturing process of the existing resistance ladder digital-to-analog conversion circuit has high precision requirements. If it is applied to a system chip, it will cause relatively high costs and require high process requirements.

[0006] In order to solve the above technical problems, the present invention provides a digital calibration method for an R-2R digital-to-analog converter, characterized in that the R-2R digital-to-analog converter includes a plurality of sequentially connected unit conversion units, and the method includes:

[0007] Connecting each unit conversion unit to the detection circuit to obtain a detection output signal corresponding to each unit conversion unit;

[0008] Obtaining actual resistance values ​​of the corresponding unit conversion units based on the detection output signals respectively, and forming an actual resistance value set of all the unit conversion units;

[0009] Obtaining a target output voltage based on an ideal digital input signal set and an ideal resistance value set of the R-2R digital-to-analog converter, and obtaining, by a minimum mean square error algorithm, an actual digital input signal corresponding to each of the unit conversion units when the error between the target output voltage and the actual output voltage is minimized;

[0010] Acquire a calibrated actual output voltage based on the actual digital input signal of each of the unit conversion units and the actual resistance value set;

[0011] The ideal digital input signal set is a set formed by the ideal digital input signals of all the unit conversion units in the R-2R digital-to-analog converter.

[0012] Preferably, the detection circuit includes a reference source, a voltage measurer and a digital signal output unit, the R-2R digital-to-analog converter also includes an amplifier, and the unit conversion unit is connected between the detection circuits, including: the reference source is connected to the voltage input terminal of the unit conversion unit, the output terminal of the unit conversion unit is connected to the input terminal of the amplifier, the voltage measurer is connected to the output terminal of the amplifier, and the digital signal input terminal of the unit conversion unit is connected to the digital signal output unit.

[0013] Preferably, connecting each unit conversion unit between the detection circuits is achieved through a switch array.

[0014] Preferably, the R-2R digital-to-analog converter includes a starting unit conversion unit and n similar unit conversion units with the same structure, the starting unit conversion unit includes a starting input resistor Ru, the similar unit conversion unit includes a resistor Ra(i) and a resistor Rb(i) connected in series, the resistor Ra(i) and the resistor Rb(i) serve as the voltage input terminal of the similar unit conversion unit, the output terminal of the resistor Rb(i) serves as the output terminal of the similar unit conversion unit, and the input terminal of the resistor Ra(i) serves as the digital input signal input terminal of the similar unit conversion unit, wherein Ra(i) represents the resistor Ra in the i-th similar unit conversion unit, and Rb(i) represents the resistor Rb in the i-th similar unit conversion unit.

[0015] Preferably, calculating the actual resistance value of the starting input resistor Ru in the starting unit conversion unit based on the detection output signal corresponding to the starting unit conversion unit includes:

[0016] The actual resistance value of the starting input resistor Ru is calculated based on the detection output signal corresponding to the starting unit conversion unit, the ideal common-mode input voltage of the amplifier, and the ideal feedback resistance of the amplifier.

[0017] Preferably, calculating the actual resistance value of the corresponding unit conversion unit based on the detection output signal corresponding to the similar unit conversion unit includes:

[0018] Based on the detection output signal when the digital input signal corresponding to each similar unit conversion unit is 1, the detection output signal when the digital input signal is 0, and the actual resistance value of the starting input resistance Ru, the actual resistance value of the resistor Ra(i) and the actual resistance value of the resistor Rb(i) in the corresponding similar unit conversion unit are obtained, and the initial value of i is 0.

[0019] Preferably, the error between the target output voltage and the actual output voltage is expressed as:

[0020] Δ=|-P·{M C -1 ·R C ·VR} / V outI -1|

[0021] Where P = [0 ... -β n ·R f β n ·R f +1], Vr(i) represents the actual digital input signal of the i-th analog conversion unit.

[0022] In order to solve the above technical problems, the present invention further provides a digital calibration device for the digital calibration method of an R-2R digital-to-analog converter, characterized in that it includes a controller and a switch array, a storage unit, and a digital signal output unit respectively connected to the controller, and further includes a reference source and a voltage measurer, wherein the voltage measurer is connected to the storage unit;

[0023] The reference source is used to provide a reference voltage source for the analog signal of the R-2R digital-to-analog converter;

[0024] The voltage measuring device is used to measure the detection output signal corresponding to each unit conversion unit in the R-2R digital-to-analog converter;

[0025] The controller is configured to obtain actual resistance values ​​in corresponding unit conversion units based on the detection output signals, and to form an actual resistance value set from a set of the actual resistance values ​​of all the unit conversion units, obtain a target output voltage based on an ideal digital input signal set and an ideal resistance value set of the R-2R digital-to-analog converter, and obtain, using a minimum mean square error algorithm, an actual digital input signal corresponding to each unit conversion unit when an error between the target output voltage and the actual output voltage is minimized, and obtain a calibrated actual output voltage based on the actual digital input signal of each unit conversion unit and the actual resistance value set, wherein the ideal digital input signal set is a set formed by the ideal digital input signals of all the unit conversion units in the R-2R digital-to-analog converter;

[0026] The storage unit is used to store the detection output signal of each unit conversion unit and store the actual resistance value of each unit conversion unit;

[0027] The digital signal output unit is used to provide a digital input signal to each unit conversion unit;

[0028] The switch array is used to connect each of the unit conversion units to between the reference source and the amplifier in the R-2R digital-to-analog converter under the control of the controller.

[0029] Preferably, the digital calibration device for the R-2R digital-to-analog converter and the R-2R digital-to-analog converter are arranged on the same chip.

[0030] Preferably, the digital calibration device for the R-2R digital-to-analog converter is not provided on the same chip as the R-2R digital-to-analog converter.

[0031] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0032] The digital calibration method for an R-2R digital-to-analog converter provided by an embodiment of the present invention connects each unit conversion unit in the R-2R digital-to-analog converter to a detection circuit to obtain a detection output signal, and then calculates the actual resistance value of each unit conversion unit based on the detection output signal. When the R-2R digital-to-analog converter performs conversion, the actual digital input signal adjusted by the R-2R digital-to-analog converter can be obtained based on parameters such as the actual resistance value and the ideal digital input signal set through a minimum mean square error algorithm. After the actual digital input signal passes through the R-2R digital-to-analog converter, a result closest to the ideal error-free target output can be obtained, thereby achieving a high-precision analog output without the need for highly matched analog devices. The method of the present invention greatly reduces the accuracy requirements for analog device matching, making it possible to design low-cost digital-to-analog converters under advanced processes. The digital calibration of the R-2R digital-to-analog converter can be achieved using relatively inexpensive devices, reducing calibration costs. The method of the present invention does not rely on the calibration of the accuracy of individual devices, but rather optimizes the calibration algorithm for overall performance, making this method more widely applicable. Moreover, the measurement phase can be completed during the mass production stage or when the chip is powered on, and there is no need to go offline for re-measurement during actual operation, which is suitable for application scenarios where long-term continuous operation is required.

[0033] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0035] Figure 1 A schematic flow chart of a digital calibration method for an R-2R digital-to-analog converter according to a first embodiment of the present invention is shown;

[0036] Figure 2 FIG2 shows a circuit diagram of an R-2R digital-to-analog converter in a first embodiment of the present invention;

[0037] Figure 3 A simplified circuit diagram is shown when the starting unit conversion unit is connected between detection circuits in the first embodiment of the present invention;

[0038] Figure 4 A simplified circuit diagram is shown when similar unit conversion units are connected between detection circuits in the first embodiment of the present invention;

[0039] Figure 5 A schematic structural diagram of a digital calibration device for an R-2R digital-to-analog converter according to a second embodiment of the present invention is shown;

[0040] Figure 6 A schematic diagram showing a structure in which a single unit conversion unit is connected to a digital calibration device for an R-2R digital-to-analog converter in a second embodiment of the present invention is shown;

[0041] Figure 7 A schematic structural diagram of a switch array in a second embodiment of the present invention is shown. DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention in detail with reference to the accompanying drawings and examples, so that the present invention can fully understand how to apply technical means to solve technical problems and achieve technical effects, and thus implement the invention accordingly. It should be noted that, as long as no conflict exists, the various embodiments of the present invention and the various features of the embodiments can be combined with each other, and the resulting technical solutions are all within the scope of protection of the present invention.

[0043] With the development of integrated circuits, more and more digital-to-analog converters are being integrated into systems-on-chip (SoCs). This requires more streamlined design approaches for digital-to-analog conversion circuits to reduce costs. At the same time, it is also necessary to minimize component deviations and mismatches caused by the manufacturing process. To improve the accuracy of resistor ladder digital-to-analog conversion circuits, existing technologies typically use expensive laser calibration equipment to calibrate components on the calibration chip, or design redundant components into the circuit to achieve error correction. Consequently, existing resistor ladder digital-to-analog conversion circuits have high process precision requirements and high costs.

[0044] Example 1

[0045] To solve the technical problems existing in the prior art, an embodiment of the present invention provides a digital calibration method for an R-2R digital-to-analog converter.

[0046] Figure 2 FIG1 shows a circuit diagram of an R-2R digital-to-analog converter in a first embodiment of the present invention; FIG2 shows a circuit diagram of an R-2R digital-to-analog converter in a first embodiment of the present invention; Figure 2 As shown, the R-2R digital-to-analog converter includes a plurality of sequentially connected unit conversion units and an amplifier, further including a starting unit conversion unit and n similar unit conversion units with the same structure. The starting unit conversion unit includes a starting input resistor Ru, and the similar unit conversion units include resistors Ra(i) and Rb(i) connected in series; Ra(i) represents the resistor Ra in the i-th similar unit conversion unit, and Rb(i) represents the resistor Rb in the i-th similar unit conversion unit.

[0047] On this basis, Figure 1 FIG1 shows a flow chart of a digital calibration method for an R-2R digital-to-analog converter according to an embodiment of the present invention; FIG2 shows a flow chart of a digital calibration method for an R-2R digital-to-analog converter according to an embodiment of the present invention; Figure 1 As shown, the digital calibration method for an R-2R digital-to-analog converter according to an embodiment of the present invention includes the following steps.

[0048] In step S101 , each unit conversion unit is connected to a detection circuit to obtain a detection output signal corresponding to each unit conversion unit.

[0049] Specifically, the detection circuit must at least include a reference source, a voltage meter, and a digital signal output unit. The specific connection method of the unit conversion unit between the detection circuit is as follows: the voltage input terminal of the unit conversion unit is connected to the reference source, so that the reference source can provide an analog signal reference voltage source for the unit conversion unit during the detection phase; the output terminal of the unit conversion unit is connected to the amplifier input terminal of the R-2R digital-to-analog converter, and the amplifier output terminal is connected to the voltage meter, so that the voltage meter can measure the detection output signal output by the amplifier during the detection phase; the digital signal input terminal of the unit conversion unit is connected to the digital signal output unit, so that the digital signal input terminal can provide a digital signal for the unit conversion unit during the detection phase.

[0050] Furthermore, each unit conversion unit can be connected to the detection circuit using a switch array. Specifically, when measuring the detection output signal corresponding to each unit conversion unit, the corresponding switch is closed to connect the corresponding unit conversion unit to the detection circuit, thereby enabling measurement of the detection output signal. The specific configuration of the switches in the switch array is conventional in the art and will not be described in detail here.

[0051] Specifically, when measuring the detection output signal of the initial unit conversion unit, only one output voltage needs to be measured to complete the calculation of the actual resistance value of the initial input resistor Ru in the initial unit conversion unit. When measuring the detection output signal of a similar unit conversion unit, the detection output signal of the corresponding similar unit conversion unit when the digital input signal is 1 and the detection output signal when the digital input signal is 0 must be measured separately. A linear equation with two variables is constructed to calculate the actual resistance value of the resistor Ra(i) and the actual resistance value of the resistor Rb(i) in the similar unit conversion unit.

[0052] In step S102 , actual resistance values ​​of corresponding unit conversion units are respectively acquired based on the detection output signals, and the actual resistance values ​​of all unit conversion units are aggregated to form a resistance value aggregate.

[0053] Figure 3FIG1 shows a simplified circuit diagram of a first embodiment of the present invention when the starting unit conversion unit is connected between the detection circuits; FIG2 shows a simplified circuit diagram of a first embodiment of the present invention when the starting unit conversion unit is connected between the detection circuits; Figure 3 It can be seen that the initial input resistance Ru is expressed as: R u =R f *V com / (V out -V com ). Where V com is the ideal common-mode input voltage of the amplifier, R f is the ideal feedback resistor of the amplifier. At this point, the actual value of the starting input resistor Ru can be calculated by simply measuring the detection output signal. Therefore, calculating the actual value of the starting input resistor Ru in the starting unit conversion unit based on the detection output signal corresponding to the starting unit conversion unit includes: calculating the actual value of the starting input resistor Ru based on the detection output signal corresponding to the starting unit conversion unit, the ideal common-mode input voltage of the amplifier, and the ideal feedback resistor.

[0054] Figure 4 FIG1 shows a simplified circuit diagram of a similar unit conversion unit connected between detection circuits in the first embodiment of the present invention; FIG2 shows a simplified circuit diagram of a similar unit conversion unit connected between detection circuits in the first embodiment of the present invention; Figure 4 It is known that: At this time, two variables, resistance Ra(i) and resistance Rb(i), need to be obtained. Therefore, the detection output signal of the similar unit conversion unit when the corresponding digital input signal is 1 and the detection output signal when the digital input signal is 0 need to be measured, and then the resistance Ra(i) and resistance Rb(i) in the similar unit conversion unit need to be solved based on a two-variable linear equation. Therefore, calculating the actual resistance value of the corresponding unit conversion unit based on the detection output signal corresponding to the similar unit conversion unit includes: obtaining the actual resistance value of the resistance Ra(i) and the actual resistance value of the resistance Rb(i) in the corresponding similar unit conversion unit based on the detection output signal of each similar unit conversion unit when the corresponding digital input signal is 1, the detection output signal when the digital input signal is 0, and the actual resistance value of the initial input resistance Ru, where the initial value of i is set to 0.

[0055] The actual resistance value of the starting input resistor Ru in the starting unit conversion unit, as well as the actual resistance values ​​of the resistors Ra(i) and Rb(i) in all similar unit conversion units, are then combined to form an actual resistance value set and stored in a memory for use when the R-2R digital-to-analog converter calibrates the digital input signal during the conversion phase.

[0056] In step S103, a target output voltage is obtained based on an ideal digital input signal set and an ideal resistance value set of the R-2R digital-to-analog converter, and an actual digital input signal corresponding to each unit conversion unit when the error between the target output voltage and the actual output voltage is minimized is obtained using a minimum mean square error (LMS) algorithm.

[0057] Specifically, based on the actual resistance value set of the R-2R digital-to-analog converter obtained previously and the ideal digital input signal set of the R-2R digital-to-analog converter, the target input digital signal to be converted and output by the R-2R digital-to-analog converter can be calculated.

[0058] For R-2R digital-to-analog converters with device errors, the goal of calibration is to find a calibrated actual digital input signal so that the output of the R-2R digital-to-analog converter with device errors can reach the target output voltage as much as possible. At this time, this can also be achieved by making the error between the target output voltage and the actual output voltage of the R-2R digital-to-analog converter as small as possible, thereby achieving the ideal design output and improving accuracy.

[0059] The principle of obtaining the error expression between the target output voltage and the actual output voltage is as follows.

[0060] refer to Figure 2 As shown, assuming that the input point voltage of the analogous unit conversion unit is represented by Vc(i) and the digital input signal of the analogous unit conversion unit is represented by Vr(i), the following relationship exists:

[0061]

[0062] ...

[0064]

[0065] in,

[0066] To facilitate calculation, make the following settings:

[0067]

[0068]

[0069]

[0070] At this time there are:

[0071]

[0072] Further make the following settings:

[0073]

[0074]

[0075] At this time, formula (1) can be simplified to

[0076]

[0077] And further by Figure 2 It can be seen that the input and output terminals of the amplifier have the following relationship:

[0078]

[0079] Assume V out Indicates the target output voltage, V outI Represents the actual output voltage, then the error between the target output voltage and the actual output voltage can be expressed as:

[0080]

[0081] In order to further simplify formula (3), we set P = [0 ... -β n ·R f β n ·R f +1], then formula (3) combined with formula (2) can be simplified to:

[0082]

[0083] By performing the minimum mean square error (MMSE) calculation on VC (i.e., equation (2)), the numerical state of VR corresponding to when Δ is at its minimum value can be obtained. That is, the digital input signal corresponding to each unit conversion unit when the error between the target output voltage and the actual output voltage is minimized can be obtained by the MSE algorithm.

[0084] Step S104 , obtaining a calibrated actual output voltage based on the target output voltage, the digital input signals of each unit conversion unit, and the resistance value set.

[0085] Specifically, after obtaining the resistance value set corresponding to the R-2R digital-to-analog converter, the actual digital input signal VR of each unit conversion unit and the target output voltage, combined with Figure 2 The circuit diagram of the R-2R digital-to-analog converter can calculate and obtain the actual output voltage of the R-2R digital-to-analog converter after calibration, thereby obtaining a high-precision analog output without the need for highly matched analog devices.

[0086] It should be noted that, to improve the applicability of the method of this embodiment, the detection phase of steps S101 and S102 and the phase of obtaining the resistance value set can be placed before the chip system is powered on or before the chip leaves the factory for detection and storage of the detection calculation results. The detection circuit can be provided on the same chip as the R-2R digital-to-analog converter so that the chip can also be tested using the detection circuit after it leaves the factory. Furthermore, the detection circuit can also be used to detect and store the detection calculation results before the R-2R digital-to-analog converter leaves the factory. The calculation and calibration process of steps S103 and S104 can be performed before the R-2R digital-to-analog converter is used to calculate the actual output voltage of the calibrated R-2R digital-to-analog converter based on the ideal digital input signal set and the resistance value set of the R-2R digital-to-analog converter.

[0087] The digital calibration method for an R-2R digital-to-analog converter provided by an embodiment of the present invention connects each unit conversion unit in the R-2R digital-to-analog converter to a detection circuit to obtain a detection output signal, and then calculates the actual resistance value of each unit conversion unit based on the detection output signal. When the R-2R digital-to-analog converter performs conversion, the actual digital input signal adjusted by the R-2R digital-to-analog converter can be obtained based on parameters such as the actual resistance value and the ideal digital input signal set through a minimum mean square error algorithm. After the actual digital input signal passes through the R-2R digital-to-analog converter, a result closest to the ideal error-free target output can be obtained, thereby achieving a high-precision analog output without the need for highly matched analog devices. The method of the present invention greatly reduces the accuracy requirements for analog device matching, making it possible to design low-cost digital-to-analog converters under advanced processes. The digital calibration of the R-2R digital-to-analog converter can be achieved using relatively inexpensive devices, reducing calibration costs. The method of the present invention does not rely on the calibration of the accuracy of individual devices, but rather optimizes the calibration algorithm for overall performance, making this method more widely applicable. Moreover, the measurement phase can be completed during the mass production stage or when the chip is powered on, and there is no need to go offline for re-measurement during actual operation, which is suitable for application scenarios where long-term continuous operation is required.

[0088] Example 2

[0089] In order to solve the technical problems existing in the prior art, an embodiment of the present invention provides a digital calibration device for an R-2R digital-to-analog converter.

[0090] Figure 5 A schematic structural diagram of a digital calibration device for an R-2R digital-to-analog converter according to a second embodiment of the present invention is shown; Figure 6FIG1 shows a schematic diagram of a structure in which a single unit conversion unit is connected to a digital calibration device for an R-2R digital-to-analog converter in a second embodiment of the present invention; FIG2 shows a schematic diagram in which a single unit conversion unit is connected to a digital calibration device for an R-2R digital-to-analog converter in a second embodiment of the present invention; Figure 5 and Figure 6 As shown, the digital calibration device for an R-2R digital-to-analog converter according to an embodiment of the present invention is primarily used to implement the real-time digital calibration method for an R-2R digital-to-analog converter described in Example 1 through a combination of software and hardware. Furthermore, the digital calibration device for an R-2R digital-to-analog converter according to an embodiment of the present invention includes a controller, a switch array, a storage unit, and a digital signal output unit respectively connected to the controller, a reference source, and a voltage meter, wherein the voltage meter is connected to the storage unit.

[0091] The reference source is used to provide a reference voltage source for the analog signal of the R-2R digital-to-analog converter. The specific working mode of the reference source is the same as that in the first embodiment, and will not be described in detail here.

[0092] The voltage measuring device measures the detection output signal corresponding to each unit conversion unit in the R-2R digital-to-analog converter. The specific detection implementation process of the voltage measuring device is the same as that of the first embodiment, and will not be described in detail here.

[0093] The controller is configured to obtain the actual resistance value of each corresponding unit conversion unit based on the detection output signal, and to form an actual resistance value set from the actual resistance value set of all unit conversion units. The controller is configured to obtain a target output voltage based on the ideal digital input signal set and the ideal resistance value set of the R-2R digital-to-analog converter, and to obtain a calibrated actual output voltage based on the actual digital input signal of each unit conversion unit and the actual resistance value set when the error between the target output voltage and the actual output voltage is minimized using a minimum mean square error algorithm. The controller is configured to obtain the actual digital input signal of each unit conversion unit and the actual resistance value set based on the actual digital input signal of each unit conversion unit when the error between the target output voltage and the actual output voltage is minimized. The ideal digital input signal set is a set formed by the ideal digital input signals of all unit conversion units in the R-2R digital-to-analog converter. The logic principle of the specific calculation process implemented by the controller is the same as the logic principle of the calculation implemented in steps S102 to S104 of the first embodiment, and is not further described herein.

[0094] The storage unit is mainly used to store the detection output signal of each unit conversion unit and store the actual resistance value in each unit conversion unit.

[0095] The digital signal output unit is mainly used to provide a digital input signal to each unit conversion unit. The specific implementation process of the digital signal output unit is the same as that in the first embodiment, and will not be described in detail here.

[0096] The switch array is mainly used for connecting each unit conversion unit to a reference power supply and an amplifier in the R-2R digital-to-analog converter under the control of the controller. Figure 7 FIG2 shows a schematic diagram of the structure of a switch array in Embodiment 2 of the present invention. The specific switch array can be set based on actual conditions, and will not be described in detail here.

[0097] It should also be noted that the digital calibration device for the R-2R digital-to-analog converter is arranged on the same chip as the R-2R digital-to-analog converter, so that the chip can be detected by a detection circuit after it leaves the factory; at the same time, the digital calibration device for the R-2R digital-to-analog converter may not be arranged on the same chip as the R-2R digital-to-analog converter, that is, the R-2R digital-to-analog converter is detected and calibrated by the digital calibration device for the R-2R digital-to-analog converter of this embodiment before leaving the factory.

[0098] The digital calibration device for an R-2R digital-to-analog converter provided by an embodiment of the present invention connects each unit conversion unit in the R-2R digital-to-analog converter to a detection circuit to obtain a detection output signal, and then calculates the actual resistance value of each unit conversion unit based on the detection output signal. When the R-2R digital-to-analog converter performs conversion, the actual digital input signal adjusted by the R-2R digital-to-analog converter can be obtained based on parameters such as the actual resistance value and the ideal digital input signal set through a minimum mean square error algorithm. After the actual digital input signal passes through the R-2R digital-to-analog converter, a result closest to the ideal error-free target output can be obtained, thereby achieving a high-precision analog output without the need for highly matched analog devices. The device of the present invention greatly reduces the accuracy requirements for analog device matching, making it possible to design low-cost digital-to-analog converters using advanced processes. The digital calibration of the R-2R digital-to-analog converter can be achieved using relatively inexpensive devices, reducing calibration costs. The device of the present invention does not rely on calibration of the accuracy of individual devices, but rather optimizes the calibration algorithm for overall performance, making this method more widely applicable. Moreover, the measurement phase can be completed during the mass production stage or when the chip is powered on, and there is no need to go offline for re-measurement during actual operation, which is suitable for application scenarios where long-term continuous operation is required.

[0099] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A digital calibration method for an R-2R digital-to-analog converter, characterized in that: The R-2R digital-to-analog converter includes a plurality of sequentially connected unit conversion units, and the method includes: Connecting each unit conversion unit to the detection circuit to obtain a detection output signal corresponding to each unit conversion unit; Obtaining actual resistance values ​​of the corresponding unit conversion units based on the detection output signals respectively, and forming an actual resistance value set of all the unit conversion units; Obtaining a target output voltage based on an ideal digital input signal set and an ideal resistance value set of the R-2R digital-to-analog converter, and obtaining, by a minimum mean square error algorithm, an actual digital input signal corresponding to each of the unit conversion units when the error between the target output voltage and the actual output voltage is minimized; Acquire a calibrated actual output voltage based on the actual digital input signal of each of the unit conversion units and the actual resistance value set; The ideal digital input signal set is a set formed by the ideal digital input signals of all the unit conversion units in the R-2R digital-to-analog converter.

2. The method according to claim 1, characterized in that The detection circuit includes a reference source, a voltage measurer and a digital signal output unit, the R-2R digital-to-analog converter also includes an amplifier, and the unit conversion unit is connected between the detection circuits, including: the reference source is connected to the voltage input terminal of the unit conversion unit, the output terminal of the unit conversion unit is connected to the input terminal of the amplifier, the voltage measurer is connected to the output terminal of the amplifier, and the digital signal input terminal of the unit conversion unit is connected to the digital signal output unit.

3. The method according to claim 2, characterized in that Each unit conversion unit is connected between the detection circuits through a switch array.

4. The method according to claim 2, characterized in that The R-2R digital-to-analog converter includes a starting unit conversion unit and n similar unit conversion units with the same structure, the starting unit conversion unit includes a starting input resistor Ru, the similar unit conversion unit includes a resistor Ra(i) and a resistor Rb(i) connected in series, the resistor Ra(i) and the resistor Rb(i) serve as the voltage input terminal of the similar unit conversion unit, the output terminal of the resistor Rb(i) serves as the output terminal of the similar unit conversion unit, and the input terminal of the resistor Ra(i) serves as the digital input signal input terminal of the similar unit conversion unit, wherein Ra(i) represents the resistor Ra in the i-th similar unit conversion unit, and Rb(i) represents the resistor Rb in the i-th similar unit conversion unit.

5. The method according to claim 4, characterized in that Calculating the actual resistance value of the starting input resistor Ru in the starting unit conversion unit based on the detection output signal corresponding to the starting unit conversion unit includes: The actual resistance value of the starting input resistor Ru is calculated based on the detection output signal corresponding to the starting unit conversion unit, the ideal common-mode input voltage of the amplifier, and the ideal feedback resistance of the amplifier.

6. The method according to claim 4, characterized in that Calculating the actual resistance value of the corresponding unit conversion unit based on the detection output signal corresponding to the similar unit conversion unit includes: Based on the detection output signal when the digital input signal corresponding to each similar unit conversion unit is 1, the detection output signal when the digital input signal is 0, and the actual resistance value of the starting input resistance Ru, the actual resistance value of the resistor Ra(i) and the actual resistance value of the resistor Rb(i) in the corresponding similar unit conversion unit are obtained, and the initial value of i is 0.

7. The method according to claim 4, characterized in that The error between the target output voltage and the actual output voltage is expressed as: Δ=|-P·{M C -1 ·R C ·VR} / V outI -1| where P = [0 … -β n ·R f β n ·R f +1], Vr(i) represents the actual digital input signal of the i-th analog conversion unit.

8. A digital calibration device for implementing the digital calibration method for an R-2R digital-to-analog converter according to any one of claims 1 to 7, characterized in that: The device comprises a controller, a switch array, a storage unit and a digital signal output unit respectively connected to the controller, and further comprises a reference source and a voltage measurer, wherein the voltage measurer is connected to the storage unit; The reference source is used to provide a reference voltage source for the analog signal of the R-2R digital-to-analog converter; The voltage measuring device is used to measure the detection output signal corresponding to each unit conversion unit in the R-2R digital-to-analog converter; The controller is configured to obtain actual resistance values ​​in corresponding unit conversion units based on the detection output signals, and to form an actual resistance value set from a set of the actual resistance values ​​of all the unit conversion units, obtain a target output voltage based on an ideal digital input signal set and an ideal resistance value set of the R-2R digital-to-analog converter, and obtain, using a minimum mean square error algorithm, an actual digital input signal corresponding to each unit conversion unit when an error between the target output voltage and the actual output voltage is minimized, and obtain a calibrated actual output voltage based on the actual digital input signal of each unit conversion unit and the actual resistance value set, wherein the ideal digital input signal set is a set formed by the ideal digital input signals of all the unit conversion units in the R-2R digital-to-analog converter; The storage unit is used to store the detection output signal of each unit conversion unit and store the actual resistance value of each unit conversion unit; The digital signal output unit is used to provide a digital input signal to each unit conversion unit; The switch array is used to connect each of the unit conversion units to between the reference source and the amplifier in the R-2R digital-to-analog converter under the control of the controller.

9. The device according to claim 8, characterized in that The digital calibration device for the R-2R digital-to-analog converter and the R-2R digital-to-analog converter are arranged on the same chip.

10. The device according to claim 8, characterized in that The digital calibration device for the R-2R digital-to-analog converter is not arranged on the same chip as the R-2R digital-to-analog converter.

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